A conventional strainer for kitchen sinks (referring to FIGS. 1 and 2) generally includes a hollow barrel 1 which has a funnel shape opening 2 with a larger diameter at the upper side and a smaller diameter at the lower side. The barrel 1 has an outer wall screwed on the bottom of the sink and a plurality of apertures 3 formed on the bottom thereof leading to a discharge tube beneath the sink. The barrel 1 has a rectangular anchor bore 4 in the center of the bottom. A disk type filter 5 made of metal is provided with filter holes 6 formed on the bottom and peripheral wall. There is a handle 7 located on the top of the center of the filter 5. The bottom of the filter 5 is coupled with a plug 8 made of rubber to stop water flow. The plug 8 has a flattened insertion strut 9 on the bottom to couple with the anchor bore 4.
When in use for stopping water discharge, insert the insertion strut 9 into the anchor bore 4 and depress, the plug 8 seals the lower side of the funnel opening 2 so that water is blocked from flowing out through the apertures 3 (referring to FIG. 2). For the filter 5 to provide filter function, pull the handle 7 upwards, and turn an angle to make the lower shoulder of the insertion strut 9 resting transversely on the anchor bore 4, the plug 8 is lifted to form a gap with the bottom of the funnel opening 2, water collected in the sink may be discharged through the filter holes 6 into the discharge tube beneath the barrel 1. In such a strainer structure, to stop water discharge through the filter 5, user has to depress downwards forcefully. To clear the residues trapped in the filter 5, the filter 5 has to be lifted and water is taken as well. As a result, the floor and sink counter often are splashed with water, and a portion of the residues could drop into the discharge tube with the water and accumulate and clog the discharge tube after a period of time. There is still room for improvement.